Energy-saving cooking appliance door having a low front temperature

ABSTRACT

A cooking appliance door having an inner and an outer wall and a perforated wall therebetween. Air flows through the door and the perforated wall, which can be substantially all or a portion of the perforated wall.

The invention relates to a cooking appliance door as claimed in thepreamble of claim 1.

Cooking appliance doors ought to fulfil a number of requirementssimultaneously: viewing of the cooked goods, minimal heat loss andminimal front temperatures while the system thickness of the baking ovendoor construction remains as minimal as possible. In particular in thecase of cooking appliances with pyrolytic self-cleaning at innertemperatures of 500° C. there is increased requirement for heatinsulating effect of the cooking appliance doors. On account of theirmultifunctional tasks cooking appliance doors can also be thermal weakspots in cooking appliance construction.

A cooking appliance door is known from U.S. Pat. No. 4,084,571, wherebya heat shield is provided between the multipart and rear part designedas trough-shaped door base and the front part designed as front framewith inset pane in the region of a pane packet mounted on the door basebetween the pane packet or the door base and the front frame or thefront glass pane. The heat shield has countless openings for improvingthe view in and is highly reflective on the side facing the cookingchamber. On the side facing away from the cooking chamber the heatshield is blackened.

DE 43 04 485 A1 also discloses a baking oven door, whereby the metallicdoor encloses a pane facing the baking oven muffle. Attached to the doorbase is a front pane. In the region opposite the metallic door floor themounted front glass pane is partially provided on its inner side facingthe cooking chamber with a reflective layer, for example withsurface-polished aluminium foil.

EP 1039 2323 A2 discloses a cooking appliance door, wherein a thermalfunctional part is arranged at a distance from the front part betweenthe front part, to which a door handle is assigned, and a back part. Thefunctional part can be a multilayer insulation film, in particularaluminium, which has integrated air chambers.

A baking oven according to the document U.S. Pat. No. 4,084,571 has asquare metallic oven muffle open to the front. This is substantiallyinsulated thermally on all sides in a manner known per se. Heatingelements known per se for heating the cooking chamber are also arrangedin the oven muffle. The oven muffle can be sealed at the front by anoven door. In general the baking oven door has a window system.

This comprises a mounted pane packet, comprising 2 to 4 generallypartially infrared-reflected panes or an additional perforated heatshield (U.S. Pat. No. 4,084,571).

The object of the present invention is to lower the front temperaturesin a cooking appliance door.

According to the invention this is achieved by a perforated wall throughwhich air flows being arranged between the inner wall and the outer wallof the door. In a cooking appliance door with an additional perforatedpartition between hot and cool side and air guiding through thisperforation lower front temperatures are achieved and heat loss flowsthrough the door construction are clearly decreased.

Further advantageous embodiments are to be inferred from the independentclaims.

In the sole diagrammatic figure a baking oven with a door designedaccording to the present invention is shown in section. A baking ovenknown per se has an oven muffle 1, in which focused heating can beapplied by way of heating elements—not shown here—and control andoperating and display elements of the cooking chamber. The cookingchamber is sealed by the door, which has a front-side outer wall 3, acooking chamber-side inner wall 5 as well as an intermediate wall 7arranged therebetween. The door is held together by different fasteningand/or mounting elements at the discretion of the expert, while theouter wall 3 and the inner wall 5 comprise glass or glasslike material.

The perforated intermediate wall 7 is arranged between the outer andinner wall 3, 5 of the door, such that forced air flow through theperforated wall 7 is achieved. The air 7 is suctioned at a lower dooredge into the door interior and suctioned at an upper door edge from thedoor interior. Because of the flowthrough of the perforated wall thethickness of the thermal limiting layer, which has a raised temperatureas gas layer near the surface, is substantially reduced and thus theheat transport is diminished by the adjacent gas cavity to the outerpane 3; ideally, the region between the thermal limiting layer and theouter pane 3 has the temperature of the suctioned air. At the same timethe perforated wall 7 through which air has flowed is cooled by theforced convection. The cooling leads to lower surface temperatures inthe perforated wall, resulting in reduced heat radiation exchange withthe opposite outer wall surface 3.

In summary, the perforation through which air flows has the followingadvantages:

The usual convection roller between two walls is hindered by theinventive measure. The air heated on the perforated intermediate wall 7is aspirated and does not make thermal contact with the cooler outerwall 3. The perforations, or the air ducts promote good thermal couplingof the wall with the air and thus efficient heat energy removal from theintermediate wall 7 to the suctioned air. Cooling the perforated walllowers its radiation emission, resulting in lower heat radiation losses.

For further reduction of the heat radiation exchange the intermediatewall 7 can be provided with a low-emitting layer (not shown) ifrequired. Thus the surface temperatures of the outside of the bakingoven doors are significantly reduced.

The system shows the best results when suctioning of the cooler airtakes place in an outer cavity of the door system—also front side—andthe aspiration of the heated air takes place in an inner cavity of thedoor system. The direction of flow of the air flowing through the dooris also against the direction of the heat loss through the door.

The perforated wall 7 can have an opening 9 either only in a transparentregion of the door or over the entire surface of the cooking appliancedoor. The position of the perforated wall inside the wall structure ofthe cooking appliance door or pane packet of the cooking appliance dooris not decisive for the physical effect. At least the cavities in frontof and behind the perforated wall 7 are to be provided for the airguiding. The suctioned air is taken from the environment outside thecooking appliance and after being heated is again discharged to theexterior on the perforated wall. According to the figure to this end thebaking oven has a cooling fan 11, which blows cool air over a frontalopen outlet shaft 13 from the baking oven. Through the injector effectas a result of suitable narrowing of the flow channel formed by thedischarge shaft 13 air is drawn from the door in a manner known per se.

Alternatively, it can also be provided that the cool air flowing throughthe intermediate wall 7 flows back at will into the cooking chamber as aresult of subpressure building up in the cooking chamber. For this ifcan for example be provided that a fumes fan and/or the cooling fan 11draws fumes out of the cooking chamber via a opening (not shown) of themuffle 1. The prerequisite for this however is a flow-technicalconnection between the door and the cooking chamber. In the event ofintroducing the heated air into the cooking chamber energy savings ispossible by using the pre-heated air; the heat loss occurring withconventional cooking appliance doors is reduced and part of the energycan be recycled to the cooking appliance.

The perforated wall 7 is understood to be a perforated glass pane, aperforated plastic pane, a perforated film or a perforated sheet etc.The perforation comprises the holes 9 or slots with a typical holediameter or gap width of 100 μm to 1 cm. The surface portion of theperforation on the wall can vary from ca. 0.1% to 50%.

In summary the forced flowthrough of the perforated wall can beaccomplished by a ventilator system placed in the cooking appliance(e.g. range hood), or a ventilator system e.g. integrated in the cookingappliance door. If required, a flowthrough of the perforated film can becreated indirectly by available air flow, e.g. through the range hoodflowing outwards over the upper edge of the cooking appliance doorutilising the Venturi effect. To avoid contamination of the perforatedwall the suctioned air can be cleaned in advance by an appropriatefilter system.

1-9. (canceled)
 10. A cooking appliance door, comprising: an inner wall;an outer wall; and an intermediate wall arranged between said inner walland said outer wall, said intermediate wall including at least aperforated wall portion through which air flows.
 11. The cookingappliance door according to claim 10, including said air enters the doorat a front side of said door.
 12. The cooking appliance door accordingto claim 10, wherein said door includes a transparent surface area andsaid perforated wall portion is provided only in said transparentsurface area.
 13. The cooking appliance door according to claim 10,including said perforated wall portion is formed from a glass pane. 14.The cooking appliance door according to claim 10, including saidperforated wall portion includes holes or slots with a typical holediameter or a slot width substantially on the order of 100 μm to 1 cm.15. The cooking appliance door according to claim 10, including thesurface of said perforated wall portion is provided on at least one sidewith an infrared-reflecting coating.
 16. The cooking appliance dooraccording to claim 10, including said air is warmed as it flows throughthe door and said warmed air guided through said perforated wall portionis deflected outwards to the atmosphere.
 17. The cooking appliance dooraccording to claim 10, including said air is forced to flowthrough saidperforated wall portion by a ventilator system present in the cookingappliance.
 18. The cooking appliance door according to claim 10,including the surface portion of said perforated wall portion issubstantially on the order of between about 0.1% and 50%.